Fix yet another missing history bounds check

src/reader/mod.rs

@@ -84,10 +84,10 @@ impl ReaderState {
         self.redraw();
     }
 
-    fn current_hist(&mut self) -> String {
+    fn current_hist(&mut self) -> Option<String> {
         let i: usize = self.history_inx.unwrap();
         let line = self.history.get(self.history.len().saturating_sub(i+1));
-        return line.unwrap().to_string();
+        return line.map(|s| s.to_string());
     }
 
     fn set_current_hist(&mut self, str: String) {
@@ -97,7 +97,7 @@ impl ReaderState {
     }
 
     fn insert_at_cursor_hist(&mut self, txt: String) {
-        let mut line = self.current_hist();
+        let mut line = self.current_hist().expect("Trying to modify a non-existent history entry");
         line.insert_str(self.cursor, txt.as_str());
         self.history_reset();
         self.set_line(line.clone());
@@ -177,6 +177,7 @@ impl ReaderState {
     pub fn read_line(&mut self) -> Result<String, ReadError> {
         use EditCommand::*;
         loop {
+            self.set_prompt(format!("{:?}> ", self.history_inx));
             let cmd = self.input_line();
             if cmd.is_err() {
                 return Err(cmd.err().unwrap());
@@ -232,7 +233,7 @@ impl ReaderState {
     pub fn history_back(&mut self) {
         let h = self.history.clone();
         let mut i = self.history_inx;
-        if i.map_or(false, |v| v+1 == h.len()) {
+        if i.map_or(h.len() == 0, |v| v+1 == h.len()) {
             bell();
             return;
         }
@@ -320,7 +321,7 @@ impl ReaderState {
     pub fn backspace(&mut self) {
         if self.history_inx.is_some() {
             if self.cursor > 0 {
-                let mut line = self.current_hist();
+                let mut line = self.current_hist().expect("Trying to modify a non-existent history entry");
                 line.remove(self.cursor-1);
                 self.move_left();
                 self.history_reset();